A seal assembly of the kind employed for retaining lubricant in and excluding foreign matter from the vicinity of bearing surfaces between relatively moving parts can comprise a face-type seal wherein sealing is accomplished by mating surfaces of relatively rotating seal parts of hard material. In seals which employ two rings of metal or other hard material relatively rotating in face-to-face contact, the production of sealing surfaces which will endure and maintain a seal throughout many hours of severe service is highly desired.
In a conventional finishing process, the sealing surface is made so that it is fairly flat. The sealing surface is then lapped with alumina grit (e.g. 15 micron). In some instances, the lapped sealing surface is polished with very fine sandpaper (e.g. 600-1200 grit alumina paper). The final polishing step can be time consuming and costly. In some instances, the final polishing step is skipped, and the manufacturer relies upon the mating sealing surfaces of the seal assembly self-honing during service. This “break-in period” can result in a joint with some initial leakage that may be unacceptable.
Commonly-owned U.S. Pat. No. 3,180,648 is entitled, “Seals.” The '648 patent describes a method for finishing seal rings of a seal assembly. The seal rings are made with their abuttable surfaces flat, or substantially flat. They are then rough lapped with their abuttable faces against a large rotating lapping table which has a spherical contour to form relieved areas for seal band reforming. This is followed by a fine lap. The rings can then be subjected to a flat lap with a compound of the same grade as the second lap to roughly form the flat sealing band. This band is then finished to a slightly conical configuration by lapping it for a brief period of time with an apparatus that comprises a circular table freely rotatable as on a spindle and having a raised annular lapping surface. The annular lapping surface is a concave lap surface in the form of a frustum of an internal cone but so shallow that its outer margin is only approximately 0.005 inch higher than its inner margin. The seal ring to be lapped is held in a chuck or adapter, the inner periphery of which is inclined to correspond to the incline which supports the torus and the seal ring in service. A torus identical to the torus used in service is employed in the apparatus. The seal ring is then rotated against the lapping surface and under pressure comparable to, and preferably substantially the same as, the pressure to which it is subjected in service.
It will be appreciated that this background description has been created by the inventor to aid the reader, and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some aspects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any disclosed feature to solve any specific problem noted herein.